In human adults, chronic periodontitis is a major cause of tooth loss. There is now abundant evidence to support the concept that accumulation of bacteria plays an important role in periodontal disease. Human polymorphonuclear leukocytes (PMN) are vital to host defenses against invading micro organisms. PMN migrate out of blood vessels and into inflamed tissues along gradients of very specific chemical signals provided by chemotactic factors. Most relevant are the low molecular weight peptides derived from the fifth component of complement as well as the bacterial chemotactic factors known as formyl peptides (FP). Exposure of PMN to formyl peptides stimulate these cells to migrate in a directed fashion (i.e. chemotaxis) and release a portion of their oxygen-derived free radicals (i.e. oxidative burst). All these functions are mediated by the binding of FP to structurally specific formyl peptide receptors (FPR) on the PMN membrane. The major objective of the proposed research is to clone, sequence, and express the cDNA coding for a putative defective FPR on PMN from a patient(s) with localized juvenile periodontitis (LJP). Studies from the applicant's laboratory have provided evidence that PMN from this patient exhibit a FP-specific chemotactic defect and have a structurally defective FPR. The applicant has been successful in cloning and expressing the cDNA and the gene coding for normal PMN FPR. Using oligonucleotide probes available in the applicant's laboratory, we will amplify LJP FPR cDNA using genomic DNA as a template and the polymerase chain reaction (PCR). PCR probes will be used to screen an LJP cDNA library. Experiments will be performed to obtain transient expression of LJP FPR cDNA by transfecting COS-7 cells. Transfected cells will be used to characterize ligand binding. Finally, normal FPR cDNA will be mutated to resemble LJP FPR cDNA to determine potential defects in ligand binding by LJP FPR. These studies should provide potential mechanisms involved in PMN dysfunction in some patients with chronic periodontitis.